Synthesis of hydrophobic hollow silica nanoparticles with synergistic structure-hydrophobicity regulation via different routes using composite silicon precursors.

Hollow silica (SiO2) has attracted extensive interest in biomedicine, adsorption, and catalysis owing to its unique structural and physicochemical properties. However, its intrinsic hydrophilicity limits its applications in oil-water separation and hydrophobic coatings, making surface hydrophobic modification a critical strategy. In this work, hollow SiO2 was synthesized via a sol-gel method using polystyrene (PS) microspheres as templates and tetraethyl orthosilicate (TEOS)/methyltriethoxysilane (MTES) as co-precursors. The TEOS/MTES ratio was optimized to regulate the shell morphology, surface roughness, and surface hydroxyl content of hollow SiO2. Subsequently, one-step and two-step silanization strategies were systematically compared to elucidate the relationship between structural evolution and hydrophobic performance. The results demonstrated that both routes could effectively impart hydrophobicity to hollow SiO2 while preserving its structural integrity and mesoporous characteristics. The two-step method endowed hollow SiO2 with superior hydrophobic performance, achieving a maximum water contact angle of 144.1°, whereas the one-step approach also rendered hollow SiO2 hydrophobic, with a contact angle of up to 126.6°. Notably, the one-step modified hollow SiO2 exhibited larger particle sizes and thicker shells, suggesting enhanced mechanical strength and structural stability. Furthermore, these samples possessed higher specific surface areas and larger internal cavity volumes, indicating excellent adsorption capacity and promising potential for applications in adsorption and catalysis. Overall, this work achieves the synergistic regulation of hollow structure and surface hydrophobicity in SiO2, yielding structurally stable hydrophobic hollow SiO2 with tunable surface properties and improved long-term stability. This study provides new insights into the surface functionalization of hollow SiO2 and establishes a theoretical foundation for its applications in oil-water separation, hydrophobic coatings, and catalysis.